/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.tomcat.util.http.parser;

import java.nio.charset.StandardCharsets;

import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.http.ServerCookie;
import org.apache.tomcat.util.http.ServerCookies;
import org.apache.tomcat.util.log.UserDataHelper;
import org.apache.tomcat.util.res.StringManager;


/**
 * <p>
 * Cookie header parser based on RFC6265
 * </p>
 * <p>
 * The parsing of cookies using RFC6265 is more relaxed that the specification in the following ways:
 * </p>
 * <ul>
 * <li>Values 0x80 to 0xFF are permitted in cookie-octet to support the use of UTF-8 in cookie values as used by HTML
 * 5.</li>
 * <li>For cookies without a value, the '=' is not required after the name as some browsers do not sent it.</li>
 * </ul>
 * <p>
 * Implementation note:<br>
 * This class has been carefully tuned. Before committing any changes, ensure that the TesterCookiePerformance unit test
 * continues to give results within 1% for the old and new parsers.
 * </p>
 */
public class Cookie {

    private static final Log log = LogFactory.getLog(Cookie.class);
    private static final UserDataHelper invalidCookieLog = new UserDataHelper(log);
    private static final StringManager sm = StringManager.getManager("org.apache.tomcat.util.http.parser");

    private static final boolean isCookieOctet[] = new boolean[256];
    private static final boolean isText[] = new boolean[256];
    private static final byte[] EMPTY_BYTES = new byte[0];
    private static final byte TAB_BYTE = (byte) 0x09;
    private static final byte SPACE_BYTE = (byte) 0x20;
    private static final byte QUOTE_BYTE = (byte) 0x22;
    private static final byte COMMA_BYTE = (byte) 0x2C;
    private static final byte SEMICOLON_BYTE = (byte) 0x3B;
    private static final byte EQUALS_BYTE = (byte) 0x3D;
    private static final byte SLASH_BYTE = (byte) 0x5C;
    private static final byte DEL_BYTE = (byte) 0x7F;


    static {
        // %x21 / %x23-2B / %x2D-3A / %x3C-5B / %x5D-7E (RFC6265)
        // %x80 to %xFF (UTF-8)
        for (int i = 0; i < 256; i++) {
            if (i < 0x21 || i == QUOTE_BYTE || i == COMMA_BYTE || i == SEMICOLON_BYTE || i == SLASH_BYTE ||
                    i == DEL_BYTE) {
                isCookieOctet[i] = false;
            } else {
                isCookieOctet[i] = true;
            }
        }
        for (int i = 0; i < 256; i++) {
            if (i < TAB_BYTE || (i > TAB_BYTE && i < SPACE_BYTE) || i == DEL_BYTE) {
                isText[i] = false;
            } else {
                isText[i] = true;
            }
        }
    }


    private Cookie() {
        // Hide default constructor
    }


    public static void parseCookie(byte[] bytes, int offset, int len, ServerCookies serverCookies) {

        // ByteBuffer is used throughout this parser as it allows the byte[]
        // and position information to be easily passed between parsing methods
        ByteBuffer bb = new ByteBuffer(bytes, offset, len);

        boolean moreToProcess = true;

        while (moreToProcess) {
            skipLWS(bb);

            int start = bb.position();
            ByteBuffer name = readToken(bb);
            ByteBuffer value = null;

            skipLWS(bb);

            SkipResult skipResult = skipByte(bb, EQUALS_BYTE);
            if (skipResult == SkipResult.FOUND) {
                skipLWS(bb);
                value = readCookieValueRfc6265(bb);
                if (value == null) {
                    // Invalid cookie value. Skip to the next semi-colon
                    skipUntilSemiColon(bb);
                    logInvalidHeader(start, bb);
                    continue;
                }
                skipLWS(bb);
            }

            skipResult = skipByte(bb, SEMICOLON_BYTE);
            if (skipResult == SkipResult.FOUND) {
                // NO-OP
            } else if (skipResult == SkipResult.NOT_FOUND) {
                // Invalid cookie. Ignore it and skip to the next semi-colon
                skipUntilSemiColon(bb);
                logInvalidHeader(start, bb);
                continue;
            } else {
                // SkipResult.EOF
                moreToProcess = false;
            }

            if (name.hasRemaining()) {
                ServerCookie sc = serverCookies.addCookie();
                sc.getName().setBytes(name.array(), name.position(), name.remaining());
                if (value == null) {
                    sc.getValue().setBytes(EMPTY_BYTES, 0, EMPTY_BYTES.length);
                } else {
                    sc.getValue().setBytes(value.array(), value.position(), value.remaining());
                }
            }
        }
    }


    private static void skipLWS(ByteBuffer bb) {
        while (bb.hasRemaining()) {
            byte b = bb.get();
            if (b != TAB_BYTE && b != SPACE_BYTE) {
                bb.rewind();
                break;
            }
        }
    }


    private static void skipUntilSemiColon(ByteBuffer bb) {
        while (bb.hasRemaining()) {
            if (bb.get() == SEMICOLON_BYTE) {
                break;
            }
        }
    }


    private static SkipResult skipByte(ByteBuffer bb, byte target) {

        if (!bb.hasRemaining()) {
            return SkipResult.EOF;
        }
        if (bb.get() == target) {
            return SkipResult.FOUND;
        }

        bb.rewind();
        return SkipResult.NOT_FOUND;
    }


    /**
     * Similar to readCookieValue() but treats a comma as part of an invalid value.
     */
    private static ByteBuffer readCookieValueRfc6265(ByteBuffer bb) {
        boolean quoted = false;
        if (bb.hasRemaining()) {
            if (bb.get() == QUOTE_BYTE) {
                quoted = true;
            } else {
                bb.rewind();
            }
        }
        int start = bb.position();
        int end = bb.limit();
        while (bb.hasRemaining()) {
            byte b = bb.get();
            if (isCookieOctet[(b & 0xFF)]) {
                // NO-OP
            } else if (b == SEMICOLON_BYTE || b == SPACE_BYTE || b == TAB_BYTE) {
                end = bb.position() - 1;
                bb.position(end);
                break;
            } else if (quoted && b == QUOTE_BYTE) {
                end = bb.position() - 1;
                break;
            } else {
                // Invalid cookie
                return null;
            }
        }

        return new ByteBuffer(bb.bytes, start, end - start);
    }


    private static ByteBuffer readToken(ByteBuffer bb) {
        final int start = bb.position();
        int end = bb.limit();
        while (bb.hasRemaining()) {
            if (!HttpParser.isToken(bb.get())) {
                end = bb.position() - 1;
                bb.position(end);
                break;
            }
        }

        return new ByteBuffer(bb.bytes, start, end - start);
    }


    private static void logInvalidHeader(int start, ByteBuffer bb) {
        UserDataHelper.Mode logMode = invalidCookieLog.getNextMode();
        if (logMode != null) {
            String headerValue = new String(bb.array(), start, bb.position() - start, StandardCharsets.UTF_8);
            String message = sm.getString("cookie.invalidCookieValue", headerValue);
            switch (logMode) {
                case INFO_THEN_DEBUG:
                    message += sm.getString("cookie.fallToDebug");
                    //$FALL-THROUGH$
                case INFO:
                    log.info(message);
                    break;
                case DEBUG:
                    log.debug(message);
            }
        }
    }


    /**
     * Custom implementation that skips many of the safety checks in {@link java.nio.ByteBuffer}.
     */
    private static class ByteBuffer {

        private final byte[] bytes;
        private int limit;
        private int position = 0;

        ByteBuffer(byte[] bytes, int offset, int len) {
            this.bytes = bytes;
            this.position = offset;
            this.limit = offset + len;
        }

        public int position() {
            return position;
        }

        public void position(int position) {
            this.position = position;
        }

        public int limit() {
            return limit;
        }

        public int remaining() {
            return limit - position;
        }

        public boolean hasRemaining() {
            return position < limit;
        }

        public byte get() {
            return bytes[position++];
        }

        public void rewind() {
            position--;
        }

        public byte[] array() {
            return bytes;
        }

        // For debug purposes
        @Override
        public String toString() {
            return "position [" + position + "], limit [" + limit + "]";
        }
    }
}
